Posted at Oct 14/2007 05:56PM:
vgorra: Yathrib, an ancient city in Saudi Arabia, later named Medina, is the second holiest city in the Islamic world. At the start of Islam, Arab communities constituted the majority of the community, however there was a small population of commercially successful Arab Jews.

In 622AS two Arab communities in Yathrib, known as the Khazraj and the Aws, invited Mohammad to flee the dangers of Mecca and seek refuge in Yathrib. However, these two communities also hoped that the arrival Muhummad would be able to bring peace to Yathrib’s contending communities of Muslims, non-Muslims Arabs, and Jews. Mohammad was able to create peace, and a treaty called the “Constitution” or “Charter of Medina,” was agreed upon.

Mohammad was then declared ruler in Yathrib. The city became the capital of the new Islamic state and its name was changed to Medina.

Posted at Oct 16/2007 10:06AM:
Ian: A couple of points to add:

1) The Arab Jewish community was actually quite large and older than the two originally pagan tribes that would in part accept Islam and the leadership of Muhammad.

2) Yathrib is best described as a collection of settlements that shared an oasis that was economically rooted in the growing of date palms. The area to the south was largely the domain of the Jewish tribes and the north that of the Aws and Khaszraj who, prior to the arrival of Muhammad as arbitor, had been engaged in bloody feuds. As such its transformation and unification under the banner of Islam allows us to see how that community began to form.

3) Archaeologically it is not well known except for these structures called the "atam" that signal how tribally organized this society was. This was a significant backdrop for how the new Muslim community was to shape a very different social order.